The present invention relates generally to wireless communication systems and in particular, to performing selection within such wireless communication systems.
Selection and distribution within wireless communication systems is known in the art. One such communication system employing selection/distribution is a Code Division Multiple Access (CDMA) communication system as described in Cellular System Remote unit-Base Station Compatibility Standard of the Electronic Industry Association/Telecommunications Industry Association Interim Standard 95A (IS-95A), which is incorporated by reference herein. (EIA/TIA can be contacted at 2001 Pennsylvania Ave. NW Washington D.C. 20006). As described in IS-95A, as a remote unit moves to the edge of a cell, it may commence communication with an adjacent base station, while the current base station continues to handle the call. The call is then handled simultaneously by both base stations. During such a scenario, the remote unit is said to be in soft handoff. Soft handoff provides diversity of forward traffic channels and reverse channel paths on the boundaries between base stations. Each base station involved in a particular soft handoff, demodulates the traffic channel frames and provides the frames to a selector function. The selector function then selects the best frame from each of the active call legs and that frame is forwarded on to the rest of the communication network. Likewise, the communication network provides frames to a distribution function that are to be transmitted to the remote unit. The distribution function distributes these frames to all base stations involved in soft handoff with the remote unit.
In current CDMA communication systems, to support soft handoff, all selection/distribution functions take place in software/hardware entities (e.g., Mobile Switching Centers (MSCs), Centralized Base Station Controllers (CBSCs), . . . , etc.) apart from base stations within the communication system. Base stations within prior-art communication systems are simply hard-wired to a single selection unit that does not vary with time. While such a configuration is adequate for existing CDMA communication systems, this configuration is inadequate for next generation CDMA communication systems, since all next generation CDMA systems virtually eliminate the need for MSCs and CBSCs. Therefore, a need exists for a method and apparatus for performing selection/distribution within a communication system that is capable of accommodating next generation CDMA communication systems.